The blue anthocyanin pigments from the blue flowers of Heliophila coronopifolia L. (Brassicaceae)

Acylated delphinidin glycosides (pigments 1– 6) and one acylated kaempferol glycoside (pigment 9) were isolated from the blue flowers of cape stock ( Heliophila coronopifolia) in the Brassicaceae along with two known acylated cyanidin glycosides (pigments 7 and 8). [Display omitted] ► Six anthocyanins and one flavonol were isolated from blue flowers of H. coronopifolia. ► Acylated anthocyanins were based on 3-sambubioside-5-glucosides of delphinidin and cyanidin. ► A blue anthocyanin–flavonol complex pigment was extracted from the blue flowers of H. coronopifolia. ► The blue pigment was composed of one molecule each of a main anthocyanin and flavonol. ► The blue pigment exhibited a molecular ion [M+1] + at 2102 m/ z. Six acylated delphinidin glycosides (pigments 1– 6) and one acylated kaempferol glycoside (pigment 9) were isolated from the blue flowers of cape stock ( Heliophila coronopifolia) in Brassicaceae along with two known acylated cyanidin glycosides (pigments 7 and 8). Pigments 1– 8, based on 3-sambubioside-5-glucosides of delphinidin and cyanidin, were acylated with hydroxycinnamic acids at 3-glycosyl residues of anthocyanidins. Using spectroscopic and chemical methods, the structures of pigments 1, 2, 5, and 6 were determined to be: delphinidin 3- O-[2- O-(β-xylopyranosyl)-6- O-(acyl)-β-glucopyranoside]-5- O-[6- O-(malonyl)-β-glucopyranoside], in which acyl moieties were, respectively, cis- p-coumaric acid for pigment 1, trans-caffeic acid for pigment 2, trans- p-coumaric acid for pigment 5 (a main pigment) and trans-ferulic acid for pigment 6, respectively. Moreover, the structure of pigments 3 and 4 were elucidated, respectively, as a demalonyl pigment 5 and a demalonyl pigment 6. Two known anthocyanins (pigments 7 and 8) were identified to be cyanidin 3-(6- p-coumaroyl-sambubioside)-5-(6-malonyl-glucoside) for pigment 7 and cyanidin 3-(6-feruloyl-sambubioside)-5-(6-malonyl-glucoside) for pigment 8 as minor anthocyanin pigments. A flavonol pigment (pigment 9) was isolated from its flowers and determined to be kaempferol 3- O-[6- O-( trans-feruloyl)-β-glucopyranoside]-7- O-cellobioside-4′- O-glucopyranoside as the main flavonol pigment. On the visible absorption spectral curve of the fresh blue petals of this plant and its petal pressed juice in the pH 5.0 buffer solution, three characteristic absorption maxima were observed at 546, 583 and 635 nm. However, the absorption curve of pigment 5 (a main anthocyanin in its flower) exhibited only one